Tank buoyancy characteristics

[vioch]

Which buoyancy characteristics are better?

weight / full / empty
28.66 / -6.83 / +0.59 in fresh water
28.66 / -4.12 / +3.3 in seawater
---
33 / -10.0 / -2.5 in seawater

I don't know the buoyancy characteristics in fresh water of the last tank -Worthingthon X7-100

The 1st one is HP Steel 12L 232bar made in Germany by Eurocylinders.

I don't fully understand the criteria for better tank buoyancy determination... so which tank has better characteristics for fresh water diving?

 

[shurite7]

Personally I find all the numbers insignificant. Understanding that AL's become positevely bouyant as the gas pressure decreases and AA's do not is much more practical.

If you can, try out different cylinders. I find an AL-80 in warm salt water works fine for me. Up here in Montana diving in cold, fresh water, and a dry suit I find my AL-80's work ok, but AL-100's work much better. I've made several dives in different cylinders to determine which I prefered.

I've met quite a few divers in my time and none of them pull out charts and numbers to determine which has better characteristics for their type of diving. They physically strapped the tank to their back and dived with it.

A friend of mine does not like the AL-100's, he prefers the AL-80's. He determined this after diving several dives with each cylinder.

C

 

[PerroneFord]

Depends on what you need. If this is for tropical diving, and you are wearing a bathing suit only or a dive skin, then you'd want the tank that was less negative.

If this is for cold water diving, and you have on a thick neoprene suit or a drysuit, you'd want the more negative tank so you wouldn't need as much lead on the weightbelt.

 

[vioch]

Tank is for cold water\drysuit diving.

Is the more negative buoyancy of the tank the better?
Could very negatively buoyant tank affect the trim (overturning diver on the back for example)?

HP 12L 300Bar Eurocylinder has 8.64lb negative buoyancy when empty in fresh water - what about its buoyancy for cold fresh water diving?

 

[TSandM]

You CAN get into trim problems with excessively negative tanks (putting you head down, like doubles can). However, it's not as common, because the negativity of a single tank is distributed over the entire tank, whereas with doubles, the manifold and regs biases the negative buoyancy toward one's head.

I have friends who dive the very negative Faber tanks and love them, because they unload the weight belt.

 

[vioch]

You CAN get into trim problems with excessively negative tanks (putting you head down, like doubles can).

I have friends who dive the very negative Faber tanks and love them, because they unload the weight belt.

TSandM how much are very negative Faber tanks negatively buoyant?

 

[Steve R]

TSandM how much are very negative Faber tanks negatively buoyant?

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Dirkadiver]

You can go to any number of websites & find buoyancy characteristics of specific tanks. If you're going to be diving a DS year round, you'll probably want as negative a tank as you can find. If you'll be back & forth between thin wetsuits & a DS, you'll want to look for the happy medium based on the least amount of exposure protection you'll wear and add a lead belt for thicker wetsuits & the DS.

 

[skynscuba]

Which buoyancy characteristics are better?

weight / full / empty
28.66 / -6.83 / +0.59 in fresh water
28.66 / -4.12 / +3.3 in seawater
---

I didn't see this one on the link you included. The change between salt and fresh is obviously wrong on this cylinder, as the difference would be more like 0.72, not 2.7

 

[vioch]

I didn't see this one on the link you included. The change between salt and fresh is obviously wrong on this cylinder, as the difference would be more like 0.72, not 2.7

Eurocylinders AG has no any information about their tanks buoyancy at the website.
I emailed them with inquiry and they provided me with the table below(Note, that the buoyancy is given in Kg (not pounds). 1kg is about 2.2lb):